For example, in the information recording medium, such as an optical disc, like a CD-ROM (Compact Disc-Read Only Memory), a CD-R (Compact Disc-Recordable), a DVD-ROM and the like, there are developed a multiple layer or multi-layer type, or dual layer type optical disc and so on, in which a plurality of recording layers are laminated on the same substrate. More specifically, such a dual layer type (i.e. two-layer type) optical disc has a first recording layer (referred to as a “L0 layer” in this application, as occasion demands), as the first layer, which is located on the front (i.e. a side closer to an optical pickup) as viewed from a laser light emission or irradiation side in recording information by the information recording apparatus, and further has a semi-transparent reflective coating or film, located on the rear thereof (i.e. a side farther from the optical pickup). As the second layer, it has a second recording layer (referred to as a “L1 layer” in this application), located on the rear of the semi-transparent reflective coating via a middle layer, such as an adhesive layer, and further has a reflective film located on the rear thereof. In preparing such a multi-layer type information recording medium, the L0 layer and the L1 layer are individually formed and pasted in the end, to thereby prepare the dual layer type optical disc at a low cost.
In the information recording apparatus, such as a CD recorder, for recording information onto such a dual layer type optical disc, the information is recorded into the L0 layer in a rewritable method or irreversible change recording method by irreversible change recording heat using heat or the like, by focusing the laser light for recording onto the L0 layer, and the information is recorded into the L1 layer in a rewritable method or irreversible change recording method by irreversible change recording heat using heat or the like, by focusing the laser light onto the L1 layer.
On the other hand, in an information recording/reproducing apparatus for recording information onto the information recording medium, such as an optical disc, the optimum power of a recording power is set by an OPC (Optimum Power Control) process, depending on the type of the optical disc and the type and recording rate of the information recording/reproducing apparatus, and so on. That is, the calibration for the recording power is performed. By this, it is possible to realize an appropriate recording operation on the optical disc. For example, if the optical disc is loaded and a writing command is inputted, data for test writing is recorded into an OPC area, with sequentially changing the optical intensity, so that a so-called “test writing process” is performed. Then, the data for test writing recorded in this manner is reproduced, and this reproduction result is judged by a predetermined estimation standard, to thereby set the optimum power (Japanese Patent No. 3159454). Moreover, even from the OPC performed at the same time of an actual recoding operation (so-called running OPC), the optimum power can be set.